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Origin and temperature dependence of radiation damage in biological samples at cryogenic temperatures

DOI: 10.1073/pnas.0905481107 DOI Help

Authors: Alke Meents (Paul Scherrer Institut) , Sascha Gutmann (Paul Scherrer Institut) , Clemens Schulze-briese (Paul Scherrer Institut) , Armin Wagner (Diamond Light Source)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Proceedings Of The National Academy Of Sciences , VOL 107 (3) , PAGES 1094-1099

State: Published (Approved)
Published: January 2010

Abstract: Radiation damage is the major impediment for obtaining structural information from biological samples by using ionizing radiation such as x-rays or electrons. The knowledge of underlying processes especially at cryogenic temperatures is still fragmentary, and a consistent mechanism has not been found yet. By using a combination of single-crystal x-ray diffraction, small-angle scattering, and qualitative and quantitative radiolysis experiments, we show that hydrogen gas, formed inside the sample during irradiation, rather than intramolecular bond cleavage between non-hydrogen atoms, is mainly responsible for the loss of high-resolution information and contrast in diffraction experiments and microscopy. The experiments that are presented in this paper cover a temperature range between 5 and 160 K and reveal that the commonly used temperature in x-ray crystallography of 100 K is not optimal in terms of minimizing radiation damage and thereby increasing the structural information obtainable in a single experiment. At 50 K, specific radiation damage to disulfide bridges is reduced by a factor of 4 compared to 100 K, and samples can tolerate a factor of 2.6 and 3.9 higher dose, as judged by the increase of Rfree values of elastase and cubic insulin crystals, respectively.

Journal Keywords: Cryocrystallography; Hydrogen Abstraction; Macromolecular Crystallography; Small-Angle X-Ray Scattering; X-Ray Radiolysis

Subject Areas: Biology and Bio-materials, Technique Development

Facility: SLS